Diagnostic approach (Figure 2.2)
The diagnostic approach to patients with chronic vomiting can vary greatly depending on the information obtained by signalment, history, and physical examination. If the animal has been receiving NSAIDs and now is vomiting blood, further diagnostics may be indicated to simply aid in determining the severity of disease and guiding the therapeutic approach.
Ideally, a minimum database should be obtained from all patients with chronic vomiting consisting of a CBC, serum biochemistry profile with electrolytes, urinalysis (UA), fecal analysis, and abdominal radiographs. In situations where results of these tests may not be readily available, a microhematocrit (PCV), total solids (TS), blood glucose, blood urea nitrogen, and if possible, a urine specific gravity can serve to guide the initial therapy. If the animal is systemically well with only mild intermittent vomiting, it is reasonable to stage the workup and treat empirically (e.g., NPO for 24 hours, easily digestible diet when food is reintroduced, ± gastroprotectants and antiemetics) pending the results of the initial diagnostic tests. Symptomatic therapy may lead to resolution of vomiting, especially if the underlying cause is transient or has been successfully removed (e.g., drugs or dietary indiscretion) and no further workup may be necessary.A more aggressive approach is warranted in those patients in which vomiting has not resolved or that present systemically ill. All patients should have a basic screen for secondary causes of vomiting (e. g., endocrine, metabolic, infectious), as well as for complications of vomiting, such as alterations in acid-base and electrolyte status. This should consist of a CBC, serum biochemistry profile with electrolytes, UA, and FeLV/FIV testing in cats. Clinicopathological findings are often normal in animals with primary gastrointestinal disease.
However, underlying renal, hepatic, or endocrine disease (e. g., hypoadren- ocortism, diabetes mellitus) are often associated with specific changes. It is a common mistake not to obtain a baseline urinalysis prior to the initiation of therapy. As fluid therapy commonly plays a role in therapy, the utility of UA especially in the assessment of renal function will be greatly reduced if obtained after a significant amount of intravenous fluids have been administered. The serum total thyroxine (T4) concentration should also be measured in all cats older than 5 years of age. If possible, additional serum should be collected and frozen for future analysis. Finally, in animals presenting with he- matemesis, a coagulation profile is warranted to screen for coagulation abnormalities, which may necessitate the administration of plasma.A fecal examination, especially in patients with concurrent diarrhea, can also be useful in determining the presence of underlying gastrointestinal parasitism, particularly ascarids in young animals and giardia in cats. Both a direct fecal smear and flotation should be performed to look for evidence of eggs and protozoal cysts or organisms. However, it is important to note that standard flotation methods are rarely useful in identifying the presence of stomach worms (e. g., Physaloptera spp. and Ollulanus tricuspis). Diagnosis of these nematodes is most commonly accomplished using Baermann concentration of vomitus or gastroscopy.3 Diagnosis of giardiasis can also be difficult with direct fecal microscopy or standard floatation alone. The gold standard in ruling out giardiasis is to obtain three negative zinc sulfate concentration centrifugations (ZSC) done on feces collected over a 3-5 day period. Commercial enzyme-linked immunosorbent assay kits to detect Giardia spp. antigen for use with dog and cat feces have a high specificity but lower sensitivity than the ZSC, and may serve as an alternative.4
Imaging studies can also be useful in the workup of a patient with chronic vomiting.
Dogs and cats should first be screened by survey abdominal radiographs to look for signs of intestinal obstruction, constipation (especially in cats), foreign objects, masses, peritonitis, visceral displacement, and free abdominal fluid or gas.5 A loop of small intestine dilated greater than twice the width of the central portion of the body of a lumbar vertebra or 3-4 times that of a rib in a dog suggests an obstructive or functional ileus.6 Delayed gastric emptying may also be evident by detection of food retained in the stomach more than 12 hours after a meal.5 In most patients with inflammatory diseases such as gastritis and IBD, routine abdominal radiographs are normal. Contrast radiography may reveal ulcers, subtle obstructions, or thickening of the gastric and /or enteric walls but has largely been replaced by the increasing use of ultrasonography and endoscopy. Abdominal ultrasound, alone or in combination with abdominal radiography, ideally should be performed in all cases where other diagnostics have failed to determine an underlying cause for the vomiting or for which a further investigation of abdominal viscera is indicated (e.g., abdominal mass visualized on radiographs, renal azotemia, increased liver enzymes, etc.). Ultrasonography may allow detection of hepatobiliary and pancreatic disease, evaluation of gastrointestinal wall thickness and peristaltic activity, characterization of obstructive lesions, and an investigation for abdominal masses. It may also facilitate fine needle aspiration to aid in the definitive diagnosis of abdominal masses, cystic lesions, and lymphadenopathy.2.2.4